For many years, various configurations for shears have been devised and proposed in an effort to provide effective cutting action on a variety of materials and over a range of thickness. It has been known that, when the cutting angle between the blades is too great, there is a tendency for the object being cut to be pushed outwardly along the blades rather than being cut. In some instances, serrated edges have been employed to minimize this squirting tendency.
Moreover, it has been known that providing a rake angle for the cutting edge will improve cutting efficiency and it has also been known that a biasing action at the point of intersection of the cutting edges of the blades will also improve cutting action.
Efforts have been made to provide a level of uniformity in the cutting angle along the length of the blade, as for example, in Shoffner U.S. Pat. No. 2,680,294 granted June 8, 1954. Efforts have also been made to provide some uniformity in the wiping action of the blade edges relative to each other as, for example, in Usborne U.S. Pat. No. 3,376,641 granted Apr. 9, 1968. Recently, there has been considerable activity in the fabrication of utility snips by stamping blade members from sheet metal with various elements of the desired configuration as, for example, those shown in Hough U.S. Pat. No. 3,974,564 granted Aug. 17, 1976; Koblick U.S. Pat. No. Des. 238,650 granted Feb. 3, 1976; and Stevenson U.S. Pat. No. Des. 239,080 granted Mar. 9, 1976.
It is an object of the present invention to provide novel and highly effective shears wherein the cutting angle defined between the cutting edges is substantially constant throughout the effective cutting length of the blade.
It is also an object to provide such shears wherein the cutting action provided by the substantially uniform cutting angle is augmented by blade edges with a desirable rake angle and which are biased together over substantially either entire length to provide the desired wiping action at the point of cutting.
Another object is to provide such shears which may be readily and economically fabricated from sheet metal to provide a durable and versatile tool.
Still another object is to provide a method for manufacturing such shears conveniently and economically.